Field of the Invention
The present invention relates to an overlock sewing machine that is capable of threading a looper thread though a looper using air pressure.
Background Art
An overlock sewing machine is provided with multiple loopers. There is a need to thread a different looper thread through each of the loopers, which requires a troublesome threading operation.
Also, sewing machines are known that are configured to supply thread using compressed air such that it reaches a looper point having a hollow structure. Such a threading operation for threading a looper using compressed air is an operation that is completely different from a sewing operation. Thus, in order to allow each component of the sewing machine to perform its operation, each component must be set to an appropriate state. For example, sewing must not be performed while a looper cover remains open.
A technique has been disclosed in Patent Literature 1, in which, in an overlock sewing machine configured to perform its operations using a single motor and to switch its operations by means of clutch switching between a pump driving operation for supplying thread using compressed air such that it reaches a looper point having a hollow structure and a main shaft driving operation for sewing, abnormal switching between the threading mode and the sewing mode is prohibited.